Process for removal of contaminants from wastes

ABSTRACT

IN A PROCESS FOR CONTINUOUS REMOVAL OF CONTAMINANTS INCLUDING CYANIDES AND TOXIC METALS SUCH AS COPPER, ZINC, SILVER, CHROMIUM, CADMIUM AND OTHERS BY THE ELECTROLYTIC PROCESS, AN ELECTROLYTIC CELL IS PARTITIONED BY A MEMBRANE INTO AT LEAST TWO ELECTROLYTIC CHAMBERS WHICH ARE FILLED WITH ELECTRIC CONDUCTORS IN A GRANULAR, FIBROUS OR SEGMENTAL FORM WITH POSITIVE AND NEGATIVE MAJOR ELECTRODES RESPECTIVELY THEREBY TO FORM AN ANODE CHAMBER AND A CATHODE CHAMBER IN ABUTTING RELATION THROUGH THE MEMBRANE. IN ACCORDANCE WITH THE PROPERTIES OF CONTAMINANTS OR THE PRESENCE OF CYANIDES, THE RINSE WATER IS SELECTIVELY LED INTO THE ANODE CHAMBER OR THE CATHODE CHAMBER TO EFFECT THE REDUCTION AND/OR OXIDATION WITH DECOMPOSITION OF THE TOXIC METALS AND CYANIDES SO THAT THE POLLUTION CONCENTRATION OF THE RINSE WATER IS LOWERED. THE RINSE WATER WITH POOR POLLUTION CONTENT IS THEN MIGRATED THROUGH THE MEMBRANE INTO THE CATHODE CHAMBER OR THE ANODE CHAMBER TO BRING A FURTHER REDUCTION AND/OR OXIDATION WITH DECOMPOSITION OF THE RESIDUAL METALS AND CYANIDES FOR REMOVAL OR DESTRUCTION OF THE CONTAMINANTS FROM THE RINSE WATER. THE ANODE CHAMBER OR THE CATHODE CHAMBER FILLED WITH THE GRANULAR OR FIBROUS CONDUCTORS WITH MAJOR ELECTRODES MAY BE REPLACED BY A POROUS CONDUCTIVE METAL SLEEVE.

Oct. 9, 1973 KA-rsuHlRo oKuBo ET AL 3,764,499

PROCESS FOR REMOVAL OF CONTAMINANTS FROM WASTES Filed Nov. 23. 1971 vssheets-sheet 1 FIG] ATSUYUKI UENO 3 Sheets-Sheet 2 1.0 pm Cell (CuComplex) (Zn 001121319X) NaCl O Eppn CN NaCl 5.11

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l/min l/min w00 11.5 .4 l/min KATSUHIRO OKUBO ET AL per m pH FR OPROCESS FOR REMOVAL OF CONTAMINANTS FROM WASTES Currwrlvfl o wm ppm Oct.9, 1973 Filed Nov. 23.

20 Spcifie ELvctzc '(dcd 4 35de@ F|G7 KATSUHIRO OKUBO ATSUYUKI ConducLvity Nagso 0 NaCl FIGS Oct. 9, 1973 Filed Nov.

KATSUHIRO OKUBO ET Al- PRocEss FOR REMOVAL 0F CONTAMINANTS 'FROM wAs'rEs3 Shoots-Shoo t, :1

IINVENTORS KATsUHlRo OKUBO ATSUYUM UENo UnitedA States Patent O3,764,499 PROCESS FOR REMOVAL OF CONTAMINANTS FROM WASTES KatsuhiroOkubo, 9-12, 6cl1ome, Higashi-Mukoujima,

sumida-lm, and Atsuyuki Ueno, 454, 1chome, Sushigaya, Setagaya-ku, bothof Tokyo, Japan Filed Nov. 23,1971, Ser. No. 201,399 Claims priority,application Japan, Nov. 26, 1970, 45/ 104,213 Int. Cl. B01d 13/02; C02b1/82; C02c 5/12 U.S. Cl. 204-151 4 Claims ABSTRACT OF THE DISCLOSURE Ina process for continuous removal of contaminants including cyanides andtoxic metals such as copper, zinc, silver, chromium, cadmium and othersby the electrolytic process, an electrolytic cell is partitioned by amembrane into at least two electrolytic chambers which are filled withelectric conductors in a granular, fibrous or segmental form withpositive and negative major electrodes respectively thereby to form ananode chamber and a cathode chamber in abutting Yrelation through themembrane. In accordance with the properties of contaminants or thepresence of cyanides, the rinse water is selectively led into the anodechamber or the cathode chamber to effect the reduction and/or oxidationwith decomposition of the toxic metals and cyanides so that thepollution concentration of the rinse water is lowered. The rinse waterwith poor pollution content is then migrated through the membrane intothe cathode chamber or the anode chamber to bring a further reductionand/or oxidation with decomposition of the residual metals and cyanidesfor removal or destruction of the contaminants from the rinse water. Theanode chamber or the cathode chamber filled with the granular or fibrousconductors with major electrodes may be replaced by a porous conductivemetal sleeve.

This invention relates to a process and an apparatus for continuousremoval of contaminants including cyanides and toxic metals such ascopper, zinc, silver, chromium, cadmium and others from the rinse Water.

Heretofore, many attempts have been brought out to remove or decomposetoxic contaminants contained in the wastes such as plating waste water,etching waste, acid rinsing waste water and other chemical treatments,for example by a chemical reaction for precipitation of the toxic metalsin the forms of hydroxide or oxide. Such the chemical reaction process,however, usually requires an installation of excessive volume and floorspace with a prolonged time for collection of deposits leaving seriousproblem of the cumbersome aftertreatment of the precipitated slugs.

In order to remove the contaminants from the wastes with an installationof relatively simple construction, it is known to use an electrolyticprocess although it usually requires an agitation of the liquid or bothin the electrolytic cell or an expansion of electrode to obtain apossibly sufficient electrolysis because of the dilute rinse water oflow electrolytic concentration following a considerable powerconsumption and an extended time for the electrolysis.

In another aspect, the chemical reaction process and the electrolyticprocess are used in combintion, notwithstanding the treating process isrendered rather complicated with increased time and cost.

To improve the foregoing disadvantages and difficulties, the inventorsfirst stood on the assumption that if the electrode area could beconsiderably expanded with the utmost access of electrodes on the basisof the conventional electrolytic cell, a sufficient electrolysis with ahigh electric current efliciency at a short time might be accom-Patented Oct.V 9, 1973 plished even for the dilute rinse water of lowelectrolytic concentration.

After an extensive research, the inventors discovered that when theelectrolytic cell is filled by the electric conductors consisting ofgranular or fibrous materials with major electrodes and a voltage isapplied between the electrodes, the granular or fibrous electricconductors have abilities to bring the electrode reactions like themajor electrodes with a remarkable expansion of the electrode area and amarvelous contraction of distance between electrodes so that thecontacting efficiency between the electrolyte or bath and the electrodesis considerably increased in cooperation with the constrained flow ofthe rinse water through the granular or fibrous electric conductors.

A further study has brought the inventors to trace the followingresults:

(l) The metals contained in the rinse water usually include lessdecomposable compounds such as a cyanide compound. Such the compounds,however, may be shifted into the decomposable condition by a previousaddition of an alkali solution of the predetermined amount to the rinsewater.

(2) When an electrolytic cell is partitioned by a membrane into an anodechamber and a cathode chamber, an alkali ion of the alkaline rinse waterled into the anode chamber migrates through the membrane into thecathode chamber entailing a considerable increase of the contactingefiiciency between the toxic metals and electrodes whereby the reductionand/or oxidation with decomposition of the metals and cyanides areimpelled while the separated alkali solution is recirculated into thesupply line of the rinse water for reuse thereof.

(3) In case of removing contaminants particularly including cyanides andtoxic metals from the rinse water of high pollution concentration, afirst electrolytic cell is preferably partitioned by a membrane into ananode chamber and a cathode chamber which is filled by solid conductorsof metallic particles with a negative major electrode while the formeris filled by solid electric conductors of graphite particles with apositive major electrode immersed in the alkali solution. The rinsewater intended to treat is first led into the cathode chamber to effecta partial reduction of the toxic metals for separation while the alkaliion in the anode chamber migrates through the membrane into the cathodechamber to render the toxic metals decomposable with a counter migrationof a part of cyanides through the membrane into the anode chamber foroxidation whereby the contents of toxic metals and cyanides in the rinsewater is reduced considerably. The rinse water thus previously treatedis further passed through a duct into the anode chamber of a secondelectrolytic cell which is partitioned by a membrane into an anodechamber which is filled by solid electric conductors of graphiteparticles with a positive major electrode and a cathode chamber ofporous conductive metal sleeve so that the cyanide ions are fairlyoxidized with decomposition and precipitation of the metal ions amongthe anode particles. The alkali solution in the rinse water when passingthrough the anode chamber migrates through the membrane into the cathodechamber for recovery. The metal ions deposited on the anode particleswhen required for cleaning may be dissolved and removed by passing anextract of ammonium chloride and ammonia through the anode particleswhile ceasing the electrolysis.

(4) In case of removing toxic metals from the rinse Water free fromcyanides, the rinse water is led into the cathode chamber of theelectrolytic cell which is partitioned into a cathode chamber filled bysolid electric conductors of metal particles with a negative majorelectrode lCe and an anode chamber of porous conductive metal sleeve toeffect the reduction of majority of metal ions for separation and theresulting efiiuent is neutralized by an addtion of the alkali solutionwhen desired and subsequently filtered out in the form of precipitates.

(5) Since a considerable expansion of the electrode area minimizes thecurrent density at the anode, the consumption of graphite conductors iseffectively saved as compared with the conventional electrolyticprocess. The consumed graphite may be supplemented by a mere additionalfilling operation of fresh graphites which enables a completeconsumption of the graphite. The electric conductors composed ofplatinum or titanium particles do not meet a substantial consumption.

(6) The high electrolysis efficiency enables to minimize the volume ofthe electrolytic cell and the efiiuent may be directly dischargedoutside of the cell. The invented electrolytic cell may be installed inthe outdoors at a low cost.

It is therefore a general object of the invention to provide a novelprocess and apparatus for prompt and tangible removal and decompositionof contaminants including cyanides and toxic metals in the wastes by anelectrolytic process.

A principal object of the present invention is to provide a process forremoval and decomposition of contaminants from the wastes whichcomprises leading the rinse water into an anode chamber which is filledby granular or fibrous electric conductors with a positive majorelectrode or into a cathode chamber which is filled by granular orfibrous electric conductors with la negative major electrode of theelectrolytic cell partitioned by a membrane to effect reduction and/oroxidation with decomposition of the contaminants and migrating theresidual contaminants through the membrane into the cathode chamber orthe anode chamber for a further reduction and oxidation withdecomposition of contaminants.

Another object of the present invention is to provide an apparatus forremoval and decomposition of contaminants from the wastes comprising anelectrolytic cell which is partitioned by a membrane into an anodechamber and a cathode chamber, said anode and cathode chambers beingfilled by granular or fibrous electric conductors with positive andnegative major electrodes respectively.

As the granular or fibrous electric conductors to be filled into theanode chamber and the cathode chamber, use may be made of conductivegranular materials such as graphite and metal particles, conductivefibrous materi-als or conductive segmental materials together with themajor electrodes and preferably with an auxiliary electrode such as anet electrode to obtain a uniform current distribution. The platinumparticles and titanium particles may also be used Ias the electricconductors in accordance with the present invention although costly.

The membrane herein used may be of usual ion-exchange membrane orparchment paper which may be stabilized by an asbestos diaphragm.

In case the electrolytic cell is designed in a cylindrical shape, theanode chamber or the cathode chamber may, preferably, be constructed bya porous conductive metal sleeve.

In consequence, it is a further object of the present invention toprovide an Iapparatus for removal and decomposition of contaminantsincluding cyanides and toxic metals from the rinse water comprising anelectrolytic cell which is partitioned by a membrane into at least twopolar chambers, one polar chamber being filled with granular or fibrouselectric conductors with a major electrode while other polar chamberbeing formed of a porous conductive metal sleeve.

The electrolytic cell of the type in accordance with the presentinvention may be connected in series for several units so that when thepollution concentration gets over the capacity of the first electrolyticcell, the

residual contaminants in the first electrolytic cell may be subjected toa further electrolytic process in the second and third cells.

Thus, a furthermore object of the present invention is to provide anapparatus for removal and decomposition of the contaminants from thewastes which comprises two or more electrolytic cells connected inseries, individual electrolytic cell being partitioned by ananionexchange membrane into an anode chamber which is filled by granularor fibrous electric conductors with a positive major electrode and acathode chamber which is filled by granular or fibrous conductors with anegative major electrode.

In the removal of the metals deposited on the anode particles or thecathode particles, an extract of approximately 15% by weight of ammoniumchloride and ammonia with pH of l0 is constrained by a circulationdevice to flow through the anode particles or the cathode particlesthereby to dissolve and remove the deposited metals and the dissolvedextract is further led to the additional electrolytic cell to obtainscraps of the metals by the electrolytic process although the solidelectric conductors deposited with the metals may be substituted withfresh electric conductors.

It is therefore an additional object of the present invention to providean apparatus for removal and decomposition of contaminants from thewastes comprising an electrolytic cell which is partitioned by adiaphragm into an anode chamber which is filled with granular or fibrousconductors with a positive major electrode and a cathode chamber whichis filled with granular or fibrous conductors with a negative majorelectrode, the electrolytic cell being associated with a circulationdevice of an extract for dissolution of the metals deposited on theanode particles or the cathode particles.

Another important object of the present invention is to provide aprocess for removal and decomposition of contaminants including cyanidesand toxic metals from the rinse water of relatively high concentrationwhich cornprises passing the rinse water through a cathode chamber of afirst electrolytic cell which is partitioned by an anionexchangemembrane into the said cathode chamber which is filled by granular orfibrous electric conductors with a major electrode and an Ianode chamberwhich is filled by granular or fibrous electric conductors with a majorelectrode immersed in an alkali solution to effect a reduction reactionof the metal ion with oxidation of cyanide ion thereby to lower thecontents of the metal ion and cyanide ion in the waste water pH of whichbeing modulated into an optimum value for decomposition of cyanide dueto the migration of the alkali solution from the anode chamber throughan anion-exchange membrane into the cathode chamber, leading the treatedrinse water of low cyanide and metal contents into an anode chamber ofthe second electrolytic cell which is partitioned by a cation-exchangemembrane into an anode chamber which is filled by graphite particlesWith a major electrode and a cathode chamber of porous conductive metalsleeve to oxidate the cyanide ion and deposit the metals on the anodeparticles and recirculating the alkali solution through the porouscathodic sleeve into the anode chamber of the first electrolytic cell.

Other objects and advantages of the present invention will becomereadily apparent and be understood from the following description ofembodiments by Way of example, reference being made to the accompanyingdrawings in which the same reference numerals designate the same orsimilar parts throughout the drawings.

FIG. l is a longitudinally sectioned elevation of the device forembodying the process in accordance with the present invention;

FIG. 2 is a pictorial front elevation of the device of FIG. 1 butconnected in series for several units;

FIG. 3 is a diagram showing a relationship between the ow rate and thecurrent exercised in connection with the waste water of 20 p.p.m.cyanide content;

FIG. 4 is a diagram showing a relationship between the flow rate and thecurrent exercised in connection with the waste water of 100 p.p.m.cyanide content;

FIG. 5 is a diagram showing an influence of NaCl concentration of theelectrolyte;

FIG. 6. is a diagram showing an influence of the specic electricconductivity on the decomposition of cyanide;

FIG. 7 is a diagram showing a relationship between the current and thecyanide-metal concentration after the electrolytic treatment;

FIG. 8 is a pictorial view of the device for removing and decomposingcontaminants from the waste water of high cyanide concentration;

FIG. 9 is a pictorial view of the device for removing and decomposingcontaminants free from cyanide; and

FIG. 10 is a pictorial view similar to FIG. 9 of the device of anotherembodiment.

Referring to FIG. 1, an apparatus for removing and decomposing the toxicmetals and cyanides from the Waste water comprises an electrolytic cell10 which is partitioned by a cation exchange membrane 12 into two polarchambers one of which is filled by graphite particles 14 with a majorelectrode 16 to form an anode chamber 18 and another polar chamber iscomposed of a porous conductive sleeve 20 of approximately 55% porosityto form a cathode chamber 22.

The anode chamber 18 is provided at its bottom portion with a waterinlet 24 and an alkali solution outlet 26 and at its top portion with aWater outlet 2S and an exhaust port 30. The cation exchange membrane 12is sandwiched by asbestos diaphragms 32 to give additional strengththereto.

EXAMPLE I A volume of the anode chamber 18 was provided at proximately2660 ml. with 55 voids of graphite particles following an effectivevolume of proximately 1330 ml. As the electrolytic bath, KCN solutionsincluding 20 p.p.m. cyanide and 100 p.p.m. cyanide were used at pH of11.5 or 12.0 with NaOH. NaCl or Na2SO4 in a proper amount was added toincrease the electric conductivity while keeping the liquid temperatureat proximately 20 C. The electrolytic bath thus modulated was urged fromthe inlet 24 into the anode chamber 18 for uniform oxidation anddecomposition reactions therein and the metal ions thus oxidized anddecomposed deposited on the anode particles 14. The alkali solutionmigrated through the asbestos diaphragm 32 and the ion-exchange membrane12 into the cathodic sleeve 22 and in turn owed down over the peripheralsurface of the cathodic sleeve 22 and directed to the recirculationsystem of the alkali solution through the outlet 26. Further, thehydrogen gas produced by the oxidation reaction was exhausted throughthe exhaust port 30 at the top of the electrolytic cell and the eiuentis ultimately discharged in almost neutralized property at pH of 6.5 to7.5. FIG. 3 illustrates the mutual relations between the flow rate, theelectric current and the cyanide concentration taken in connection withthe 20 p.p.m. cyanide solution. FIG. 4 also shows the relations betweenthe ow rate, the electric current and the cyanide concentration taken inconnection with the 100 p.p.m. cyanide solution. In both examples, ithas been appreciated that the residual cyanide concentration was loweredto 10-1 p.p.m. and even 10-2-10-3 p.p.m. at the lowermost with theproviso that the flow rate and the electric current have suitablevalues. Considering the relations between the ow rate and the electriccurrent with reference to FIG. 3 for providing a certain proper residualcyanide concentration, the curves 40 to 48 provide a substantiallyconstant ratio between the flow rate and the electric current while thecurves 34 to 3S provide an irregular ratio therebetween. FIG. 4 showsthe similar results. These data suggest that the tlow rate against theetfective volume or the liquid content of the anode charnber is animportant factor. That is, it is presumed that an excessively shortresidence in the electrolytic cell lowers the contacting eiiciencybetween the electrode and the solution. In case of 100 p.p.m. cyanideconcentration, the residual cyanide concentration had a substantiallylinear value with the proviso that the iiow rate is proximately 1/5 timethat of the 20 p.p.m. cyanide concentration which implies thatconsideration of the ratio between the concentration and the flow rateis suiiicient. FIG. 5 illustrates the example wherein the NaCl contentsin the electrolytic bath were varied. The diagram shows that an increaseof the NaCl concentration impels the decomposition of the cyanide,although an addition of NaCl is not absolutely necessary as best shownin FIG. 6. Instead of NaCl, use may be made of Na2SO4 preferably with aspecilic electric conductivity of proximately 5 X10-@ 1 cmi1 andpositively 10X10-3Q-1 cm.1 or more.

The concentration of sodium chloride in the anodic bath was analyzed forthe cases wherein the sodium chloride of from 10 to 30 times thetheoretical amount required for the decomposition was added. Theanalysis showed that the chloride ion of higher concentration brings amore efliciency, notwithstanding the concentration of 10 to 20 times thetheoretical amount is preferred in an economical point of view. Afurther comparative experiment was exercised between an anodic bathcontaining the chloride ion and that free from the chloride ion with theresult that the anodic bath containing chloride ion brought a highefficiency particularly at the low electric current density. Since,however, the waste water even free from the chloride ion often containsthe electrolytes such as sodium sulfate, sodium carbonate, sodiumhydroxide and others, it has been appreciated that the decomposition ofalmost the same efficiency is accomplished with the proviso that thespecic electric conductivity thereof is proximately 5 1013 or 10X10-30-1 crn.-1 or more. Moreover, the temperature ranges of the wastewater were measured at 15 C., 250 C. and 45 C. The decompositioneiliciency at each range was substantially linear level and nosubstantial influence of the temperature could be traced.

Now again back to FIG. 2 which shows several electrolytic cells similarto the cell as shown in FIG. 1 connected in series through a pipe 50. Inaccordance with this installation, when the pollution concentration ofthe waste water were measured at 15 C., 25 C. and 45 C. A, the wastewater containing residual contaminants including undecomposed cyanideion and metal ion may be further subjected the electrolysis at thesecond cell B for additional removal and decomposition operations andwhen desired led into the third cell C for the perfect removal anddecomposition of cyanide ion and toxic metal lon.

FIG. 8 shows an alternative embodiment of the multiple type electrolyticcell system as shown in FIG. 2 particularly designed for treatment ofthe water of the higher cyanide concentration wherein a rst electrolyticcell 52 is partitioned by an anion exchange membrane 54 to provide acathode chamber 56 and an anode chamber 58. The cathode chamber 56 islled with the conductive metal particles 60 with a negative majorelectrode 62 while the anode chamber 58 is iilled graphite particles 64immersed in an alkali solution with a positive major electrode 66encircling the graphite particles 64. The cathode chamber 56 is providedat its bottom portion with a waste water inlet 68 and at its top portionwith an outlet 70 which is further connected to a pipe 72 communicatinginto a bottom inlet 74 of a second electrolytic cell 76 of thesubstantially same construction as that shown in FIG. l. From a receiver7 8 for the alkali solution, a feed pipe is led into the anode chamber60 of the first electrolytic cell S2. The second electrolytic cell 7 6is provided in abutment relation with a storage tank 82 for the rinsingextract from the bottom of which a pipe 84 is derived into the bottom ofthe anode chamber 86 of the second electrolytic cell 76. A pipe 88 isderived from the top of the anode chamber 86 into the storage tank 82.

In the typical operation of removing and decomposing cyanide ion andmetal ion from the waste Water with the foregoing device, the wastewater is first introduced into the cathode chamber 56 of the firstelectrolytic cell 52 wherein the toxic metals in the waste water arepartially subjected to the reduction reaction for separation in the formof slugs which are deposited on the metal particles 60. A part of alkalisolution reserved in the anode chamber 58 migrates through the anionexchange membrane 54 into the cathode chamber 56 to modulate thehydrogen ion concentration (pH) of the waste water to proximately 10 to12. On the other hand, cyanides in the waste water are partially migratethrough the anion exchange membrane 54 into the anode chamber 58 foroxidation under the influence of the anodic particles 64. Thus, theconcentrations of toxic metals and cyanides in the waste water arelowered considerably with the moderation of pH to the optimum value of10 to 12 for the oxidation of cyanide.

The waste water treated in the first electrolytic cell 52 is then ledthrough the pipe line 72 into the anode chamber 86 of the secondelectrolytic cell 76 wherein the residual cyanide ions are oxidized andalso the remaining metal ions are decomposed for precipitation on theanodic particles 90. The alkali solution contained in the waste watermigrates through the cation exchange membrane 92 and flows down alongthe periperhal surface of the porous cathode sleeve 94 into the receiver78 and then fed back into the anode chamber 58 of the first electrolyticcell 52 to establish a recirculation system of the alkali solution. Theeffluent is discharged outside of the device through the drain pipe 96.The storage tank 82 reserves an extract of ammonia chloride and ammoniawhich is circulated into the anode chamber 86 of the second electrolyticcell 76 when rinsing the anodic particles 90 deposited with contaminantsby ceasing the electrolytic operation. By this operation, the toxicmetal slugs such as copper, zinc, nickel, cadmium and the like aredissolved and the dissolution thus obtained is further subjected toanother electrolytic process to separate the metals and the purifiedextract is fed back into the storage tank 82 for reuse.

EXAMPLE II The extract in 10 liter was passed through the anodicparticles to dissolve about 80% by weight of slugs out in severalminutes. The metal concentrations of the extract were 21.3 ppm. copper,16.2 p.p.m. zinc and 6.3 ppm. nickel. The extract was further subjectedto the electrolytic process at the cathode chamber to separate themetals out with substantially the same concentrations as the originalextract. Thus, the concentration of the extract was lowered to l ppm. orless. FIG. 7 shows the relation between the electric current and theconcentrations of cyanide and metal after treatment exercised inconnection with the complex cyanate solution of copper and zinc. Thecopper and zinc concentrations in the solution after treatment werelowered to 0.01 to 0.02 ppm. Although the cyanide concentration isinferior to the alkali cyanide solution alone, the current efhciency gotover 80%.

FIGS. 9 and 10 show devices for removing and decomposing the toxicmetals free from the cyanide from the waste water.

The device shown in FIG. 9 has substantially the same construction asthe first electrolytic cell of the device of FIG. 8. In this embodiment,the electrolytic cell 98 is partitioned by the anion exchange membrane100 into a cathode chamber 102 which is filled with conductive metalparticles 104 with a negative major electrode 106 and an anode chamberof porous conductive metal sleeve 108. On passing of the waste waterthrough the cathodic metal particles 104, the metal ions are depositedon the metal particles by the reduction reaction whereas the sulfateion, the chloride ion and the like migrate through the anion exchangemembrane for conversion into a sulfuric acid and a hydrochloric acid andthe like respectively and are discharged through the porous anodicsleeve for neutralization by an addition of alkali solution. Theefiiuent is discharged from the top of the cathode chamber 102 through adrain pipe 110 to the outside of the device. If the effluent is notfairly neutralized, it is preferable to add a suitable amount of alkalisolution to the efiiuent for neutralization to obtain pH of proximately7. The negligible amount of the residual metals in the waste isprecipitated and filtered out.

In the electrolytic cell as best shown in FIG. 10, the porous anodicsleeve 108 used in the electrolytic cell of FIG. 9 is replaced by ananodic cell 112 which is filled with a liquid 114 adapted to bubble thegas produced the oxidation reaction.

In accordance with the present invention, a sufficient electrolysis maybe accomplished by a device of simple construction which enables tocarry out continuous and effective removal and decomposition ofcontaminants including cyanides toxic metals and others from the wastesof high as well as low concentration.

While certain preferred embodiments of the invention have beenillustrated by way of example in the drawings and particularlydescribed, it Will be understood that modifications may be made in theconstructions and that the invention is no way limited to theembodiments shown. For example, when the anode chamber of theelectrolytic cell is filled by granular, iibrous or segmental conductorswith a major electrode the cathode may be formed of a plate or sleeveconfiguration Whereas when the cathode chamber is filled by granular,fibrous or segmental conductors an anode may be formed of a plate orsleeve configuration or the cathode and anode chambers may beselectively filled with the granular, fibrous or segmental conductors asthe case may be.

We claim:

1. A process for removal and decomposition of contaminants from thewaste water which comprises leading the waste water into a cell having afirst major electrode chamber which is filled by granular or fibrouselectric conductors and a major electrode, said first major electrodechamber being separated from a second electrode chamber of oppositepolarity by an ion exchange membrane, applying a potential across a cellconstituted by said first and second electrode chambers to eiiect anelectrolytic reaction with decomposition of the contaminants in thefirst major electrode chamber and with migration of the residualcontaminants through the membrane into the second electrode chamber forfurther electrolytic reaction with decomposition.

2. The process of claim 1 wherein said first major electrode chamber isthe anode chamber and said second electrode chamber is the cathodechamber.

3. The process of claim 1 wherein said rst major electrode chamber isthe cathode chamber and said second electrode chamber is the anodechamber.

4. A process for removal and decomposition of contaminants includingcyanides and toxic metals from' the waste water of high concentrationwhich comprises passing the waste water through a cathode chamber of afirst electrolytic cell which is partitioned by an anionexchangemembrane into the cathode chamber which is filled by granular or fibrouselectric conductors with a major electrode and an anode chamber which isiilled by granular or fibrous electric conductors with a major electrodeimmersed in an alkali solution to effect a reduction reaction of themetal iorr with oxidation of cyanide ion with migrations of a part ofalkali solution from the anode chamber through the anion-exchangemembrane into the cathode chamber and of a part of cyanides from thecathode chamber through the anion-exchange membrane into the anodechamber for oxidation, leading the treated waste water of loweredcyanide and metal concentration into an anode chamber of a secondelectrolytic cell which is 10 partitioned by a cation-exchange membraneinto an anode 2,788,319 4/ 1957 Pearson 204-151 chamber which is lled bygranular and brous conductors 2,997,430 8/ 1961 F yn 204-151 with amajor electrode and a cathode chamber of porous 3,135,674 6/ 1964Ruetshi 204-151 conductive metal sleeve to oxidate and decompose the3,296,111 1/ 1967 Miller et al 204-151 X residual cyanide ion and metalion and recirculating the 3,457,152 7/ 1969 Maloney, Jr. et al. 204--131alkali solution through the porous metal sleeve into the 5 3,616,356 10/1971 Roy 204-152 anode chamber of the rst electrolytic cell.

JOHN H. MACK, Primary Examiner References Cited A. C. PRESCOTT,Assistant Examiner UNITED STATES PATENTS 10 4698,292 4/1902 Kendall204-110 USC1XR- 2,259,046 10/1941 Roberts 204-151 204--131, 149, 180P

